Reliability improvement to copper damascene structures using buried capping layer

A buried capping layer (BCL) of undoped silicate glass (USG) was incorporated into Cu damascene structures to improve electrical reliability. With carbon-doped silicon oxide (SiOC) as intermetal dielectric, the results showed that a BCL of 100 Angstrom thickness successfully improved breakdown strength two-fold and reduced leakage by 1 order of magnitude to within the specification of 10(-8) A/cm(2) (at 25degreesC). The incorporated BCL of 100 A thickness increased the overall parasitic capacitance by merely 2%, compared to conventional structures without BCL. The BCL is therefore a promising candidate in improving the overall electrical reliability of interconnects.